I recently bought an 05 sportsman500 ho. She cranks up just fine but the minute I put it in gear the starter will engage . If I grab a hand full of the left brake the starter will disengage until I let go of the brake. So I figured it must be cross feeding through the light system somehow, so I removed the light fuse and it no longer does it. I would love to have my lights again. Anybody have any ideas what might be causing this?

 

Think it might be more related to either the starter solenoid malfunction or even an ecm problem.I'd check all connections from the battery to the solenoid,plus are you sure it's the starter continuing to run or could it possibly be the starter bendix hanging up after it cranks?

 

The starter will disengage after it is running and will try and reegage when you put it in gear. I've never seen anything like this before.

 

Neither have I.. I'd pull every connection under the front panel and use some dielectric grease and see if that helps. Same thing on the left control switch. Still possible the ecm is screwing up because of all that's in the blame thing. You might disconnect it grease the connectors and reinstall them. Maybe rebooting it can help.
Plus thinking about the solenoid again.. From the ignition switch there is a white/red wire that goes directly to the solenoid,powered up when starting,then causes the solenoid to transfer power from the battery cable to the starter cable. I'd pull the ignition switch connector,grease it,plus spray some wd 40/PB blaster in the key hole and work the ignition switch back and forth. Possibly the switch itself may be the problem?

 

I was thinking the same thing about the key switch so I replaced it with a new unit. I also just tried to let the ecm rest itself by unplugging it for a while, that was a nogo also.

 

Then the ecm or the solenoid itself would be what I'd be checking next as the only way the starter gets power is through the solenoid. Hopefully you've had the ecm replacement recall done,but even if you have, I've had multiple replacement ecms fail for one reason or another also. Can't miss if you haven't.(Plus no cost to you) It's a black finned Chinese module replaced by this one. http://www.ebay.com/itm/2004-2006-Polaris-Sportsman-and-Scrambler-400-450-500-OEM-Surepower-ECM-2005-PDM-/171576768506?hash=item27f2c5b7fa&vxp=mtr

 

The only way the starter solenoid can get power is from the key switch , try removing the w/r wire from the starter solenoid and put a meter or even a 12 volt light bulb from ground to the disconnected w/r wire and turn the key to on position , there should be no light/power until you turn key to crank position . If you have power with the key in run position then start checking the wiring harness for a rub through where the wires are touching each other .
Another thing to check - did the previous owner do any wiring modifications ?

 

Did it get the ECM brain box recall done yet? ATV: Polaris Ind. expands recall of ATVs those things can cause some strange problems .